Lebanon's Supreme Islamic Shi'ite Council has condemned the execution of a prominent Shi'ite cleric in Saudi Arabia, saying it was a "grave mistake".
Saudi Arabia executed Sheikh Nimr al-Nimr and 46 other people.
Most of those executed were convicted of leading or carrying out a series of al Qaeda attacks in Saudi Arabia after 2003, but they also included some members of the Shi'ite minority convicted of attacks on police during protests from 2011-13.
"The execution of Sheikh Nimr was an execution of reason, moderation and dialogue," the council's vice president Sheikh Abdel Amir Qabalan said in a statement.
Yemen's Houthi movement, the Arabian Peninsula's most powerful armed Shi'ite group and a major Saudi foe, also mourned the cleric as a "holy warrior".
"The Al Saudi family executed today the holy warrior, the grand cleric Nimr Baqr al-Nimr after a mock trial ... a flagrant violation of human rights," an obituary on the Houthis' official Al Maseera website said.
In Iran, prominent state-affiliated cleric Ahmad Khatami said the execution was to be expected of "criminal" Saudi Arabia.
In Iraq, a Shi'ite ruling coalition MP said the execution aimed to "set the region on fire".
Khatami, one of the most senior clerics in Shi'ite-ruled Iran, said in an interview with the Mehr news agency that Nimr's execution reflected the "criminal" nature of the Saudi ruling family.
"I have no doubt that this pure blood will stain the collar of the House of Saud and wipe them from the pages of history," Khatami, a member of the Assembly of Experts and a Friday prayer leader, was quoted as saying by Mehr.
"The crime of executing Sheikh Nimr is part of a criminal pattern by this treacherous family ... the Islamic world is expected to cry out and denounce this infamous regime as much as it can," Khatami added.
Nimr's brother said the family was shocked by news of the execution but hoped any reaction would be peaceful.
Nimr and six other Saudi Shi'ites, including Mohammed al-Nimr's son, Ali, were sentenced to die and to have their bodies publicly displayed, the most severe penalty available to judges in the strict Sunni majority kingdom.
They were among 47 people put to death by Saudi Arabia on Saturday for terrorism, an apparent message to both Sunni Muslim jihadists and Shi'ite anti-government protesters that the conservative Islamic kingdom will brook no violent dissent.
Mohammed al-Nimr said residents of Saudi Arabia's eastern al-Qatif region, where most of the country's mainly Shi'ite Muslim minority live, were alarmed by the news.
"We were expecting and hoping that the voice of moderation and political settlements would prevail," Mohammed al-Nimr told Reuters. "We were shocked by this harsh news.
"Sheikh Nimr enjoyed high esteem in his community and within Muslim society in general and no doubt there will be reaction. We hope that any reactions would be confined to a peaceful framework," he said. "Enough bloodshed."
Nimr had long been regarded as the most vocal Shi'ite leader in Qatif, willing to publicly criticise the Al Saud ruling family and call directly for elections.
Iran's foreign ministry spokesman accused Saudi Arabia of supporting terrorism and executing its opponents.
"The Saudi government supports terrorists and takfiri (radical Sunni) extremists, while executing and suppressing critics inside the country," Foreign Ministry spokesman Hossein Jaber Ansari was quoted as saying by state news agency IRNA.
